Field of the Invention
The invention relates to the infrared control technology, and more particularly to an infrared circuit for a single battery and a remote controller using the same.
Description of the Related Art
FIG. 1 is a circuit diagram showing a conventional device having an infrared emitting function. Referring to FIG. 1, the device having the infrared emitting function comprises a microcontroller 101, an IR LED 102 and at least two serially connected batteries 103. The microcontroller 101 has an input/output pin P01 coupled to an anode of the IR LED 102. The microcontroller 101 outputs a pulse signal PS to the IR LED 102 through the input/output pin P01.
In the prior art, the threshold voltage of the IR LED 102 ranges from 1.0V to 1.5V, and the ordinary battery has the voltage of about 1.5V when no load is present. A no-load voltage of an unused new battery may approach 1.65V, and the voltage of the battery continuously decreases with the use of the battery. The battery may be regarded as failed after the voltage thereof is lower than 1.0V or 0.9V. When the battery is coupled to the load, the voltage thereof is decreased with the increase of the output current, and is often decreased to the voltage between 1.1V and 1.3V when an ordinary load is applied. The voltage of one battery may be higher than or lower than a threshold voltage of an infrared emitting tube. When the voltage is higher than the threshold voltage, the exceeded voltage value is too low. Thus, the current flowing through the IR LED is smaller, thereby causing the too-short emitting distance that cannot be accepted by the user. In addition, when the battery is used for a period of time, the voltage of the battery is lower than the threshold voltage of the IR LED. At this time, the IR LED cannot emit the infrared rays. Thus, the device with the infrared emitting function typically needs at least two batteries connected in series.